Burner and method for partially oxidizing liquid, carbon-containing fuel

ABSTRACT

A burner for the partial oxidation of liquid, carbonaceous fuel with steam and an oxygen-containing gas a well as the process in which this burner is used, wherein the parts of the outlet orifice of the burner directed towards the combustion chamber are wholly or partly provided with a coating or with a diffusion layer for protection against thermal load and/or corrosion.

FIELD OF THE INVENTION

This invention relates to a burner for the partial oxidation of liquid,carbonaceous fuel with steam and an oxygen-containing gas, and to theprocess for producing synthesis gas by partial oxidation of said fuels,in which the burner according to the invention is used.

PRIOR ART

A known process for the partial oxidation of liquid, carbonaceousfeedstocks for the production of synthesis gas for example is the Lurgiprocess as described in Ullmann's Encyclopedia of Industrial Chemistry,6th Edition, Volume 15, Chapt. 3.2.2.

In such processes, the hydrocarbonaceous feedstock stream, e.g. heavyoil, together with the oxygen-containing oxidizing agent, e.g. airenriched with oxygen, and possibly a moderator (mostly steam or carbondioxide) is converted into a synthesis gas chiefly consisting of carbonmonoxide and hydrogen in a reactor space (combustion chamber) attemperatures of 1200 to 1500° C. and high pressures, between 30 and 75bar.

The reactor is equipped with one or more burners which in general areinstalled at the head of the reactor such that their flame is verticallyguided into the reactor from top to bottom, so that only the lower endof the burner throat protrudes into the combustion chamber and isexposed to the high temperatures and the corrosive atmosphere of thecombustion chamber. Such burner is described in DE 198 60 479 C1 and inDE 199 31 373 A1.

The high temperatures and corrosive gases obtained in these processesfor producing synthesis gas limit the durability of the burners.Therefore, at least the components of the burners subjected to highloads are fabricated from so-called superalloys. These are hightemperature resistant alloys, such as high-carbon nickel-chromium-ironalloys. Fundamental statements on superalloys can be found in RomppsChemie-Lexikon, 8th edition, Franckh'sche Verlagshandlung, Stuttgart.

Beside the selection of particularly robust construction materialsnumerous constructive methods have been developed to extend the servicelife of the burners.

In EP 0 545 281 B1 it is proposed to line the end face of the burnerthroat with a layer composed of individual ceramic platelets arrangedone beside the other.

In EP 1 284 234 A2 it is proposed to divide the inner burner tube intotwo halves releasably connected with each other, wherein only the lowerhalf facing the end face of the burner is made of a particularly hightemperature resistant and high-melting metal alloy. The end face of theouter burner tube is equipped with a space for the passage of a coolingmedium and in addition the burner throat protruding into the reactor issurrounded with cooling coils.

DE 601 20 674 T2 proposes the installation of an annular heat shield onthe end face of the burner throat, which is made of a material with ahigh melting point.

What is disadvantageous in the previously proposed solutions forextending the service life of the burner is the fact that they intervenein the construction of the burner throat, so that in the construction acompromise must be found between the actual function of the burner andthe measures for protecting the same against corrosion.

DESCRIPTION OF THE INVENTION

Therefore, it has been the object to find a solution for extending theservice life of the burner, which rather does not intervene in theconstruction of the burner and can be carried out economically.

The solution of the object according to the invention substantially canbe derived from the characterizing features of claim 1 in conjunctionwith the features of the generic part. Further advantageous aspects ofthe invention can be taken from the sub-claims. This invention alsorelates to a process for the partial oxidation of liquid, carbonaceousfuel with steam and an oxygen-containing gas, in which the burneraccording to the invention is used.

This object is solved in that the parts of the outlet orifice directedtowards the combustion chamber are wholly or partly provided with acoating or with a diffusion layer for protection against thermal loadand/or corrosion.

This inventive solution of the object was induced by the proven practicein the construction of hot gas turbines to provide the parts exposed tohigh temperatures and corrosive gases with a protective ceramic layer,as is reported e.g. in DE 35 43 802 A1.

PREFERRED ASPECTS OF THE INVENTION

In accordance with a preferred aspect of the invention the burneraccording to the invention is provided with a coating of an adhesivelayer and a heat insulation layer, which each are applied by a thermalspraying method, such as plasma spraying, wherein the adhesive layerconsists of the metal mixture MCrAlY (M represents at least one of theelements Ni, Co, Pt or Pd) and wherein the heat insulation layerpreferably consists of an oxidic spraying material, in particular ofZrO₂. This combination of materials was found to be particularlyeffective with regard to the extension of the service life of theburner.

In a further aspect of the invention it is provided that by alitizing,chromizing or siliconizing merely a diffusion layer is produced in thesurface of the workpiece. The separate heat insulation layer is omitted,which contributes to the constructive simplicity of the burner accordingto the invention.

In accordance with a particularly preferred aspect of the invention theburner designed according to the invention is wholly or partly providedwith a combination of a coating for protection against thermal load anda diffusion layer on its parts of the outlet orifice directed towardsthe combustion chamber. In this way, a particularly marked extension ofthe service life and the related operating cost advantages are achieved.

This invention also relates to a process for the partial oxidation ofliquid, carbonaceous fuel with steam and an oxygen-containing gas, whichis characterized in that at least one burner according to at least oneof claims 1 to 4 is used. Details of the procedure and constructivedetails of the burner are known to the skilled person and describedalready for example in the documents DE 19931373 A1, DE 19860479 C1, DE10152686 A1 and DE 10156980 A1, the disclosure of which is herewithincluded in the present application by reference.

Further developments, advantages and possible applications of theinvention can also be taken from the following description ofembodiments and the drawings. All features described and/or illustratedform the invention per se or in any combination, independent of theirinclusion in the claims or their back-reference.

In the drawing:

FIG. 1 shows the arrangement of the burner according to the invention inthe combustion chamber,

FIG. 2 shows the position and the layered structure of the protectivelayer according to a first preferred aspect of the invention,

FIG. 3 shows the position and the layered structure of the protectivelayer according to a second preferred aspect of the invention,

FIG. 1 shows how the throat (1) of the burner extends through thereactor wall (3) into the combustion chamber (4) of the reactor with thelower end of the outer burner tube (2). In this example, the throat ofthe burner (1) is constructed of two concentric tubes. The inner tube(5) conveys a mixture (6) of carbonaceous fuel and steam, the outer tube(2) conveys the oxygen (7) necessary for the combustion and/or partialoxidation, which is possibly mixed with steam or carbon dioxide. FIG. 1shows the inner (5) and outer (2) tube ends of the burner throat by wayof example as straight tube pieces. Other tube shapes are, however, alsopossible, such as tubes conically tapering towards the tube end orwidening tubes. It is also possible that the outer tube (2) is providedwith a cooling chamber (9) in which a coolant is contained. In thisexample shown in FIG. 1 the end face of the outer tube (2) directed intothe combustion chamber (4) is provided with a protective layer (8) whichaccording to the invention can be a coating or a diffusion layer. Ofcourse, the lower end face of the inner tube (5) can also be providedwith such protective layer, which is not shown in FIG. 1.

As indicated in FIG. 1, the protective layer (8) can not only cover theend face, but also the surfaces in the inner or outer region of the tubeor tubes of the burner throat.

FIG. 2 shows the layered structure of the protective layer ((8) inFIG. 1) according to claim 2.

In the aspect of the invention according to claim 2, an adhesive layer(11) and a heat insulation layer (13) each are applied onto theworkpiece (10) by a thermal spraying method, such as plasma spraying,wherein the adhesive layer (11) consists of the metal mixture MCrAlY (Mrepresents at least one of the elements Ni, Co, Pt or Pd) and whereinthe heat insulation layer (13) preferably consists of an oxidic sprayingmaterial, in particular of ZrO₂. The surface (12) of this adhesive layer(11) additionally is enriched with aluminum and silicon atoms in itssurface by a diffusion treatment, by so-called alitizing/siliconizing.

Thermal coating methods, such as plasma spraying, useful for thesolution of the object are described in Ullmann's Encyclopedia ofIndustrial Chemistry, 6th Edition, Volume 21, Chapt. 5.

The fact that the durability of the protective layer is improved bypriming by means of an adhesive layer of this type is known to theskilled person for example from U.S. Pat. No. 4,321,310. In thedevelopment of the present invention MCrAlY spraying material with thetrade name SICOAT 2464 has been used successfully.

FIG. 3 shows the structure of the protective layer ((8) in FIG. 1)according to claim 3.

The variant of the invention according to claim 3 consists in that acoating of the workpiece (10′) is omitted and instead the surface to beprotected merely is subjected to a diffusion treatment, wherein aluminumand/or silicon and/or chromium atoms diffuse into the surface (12′).These processes are known to the skilled person as alitizing,siliconizing and chromizing. The fundamentals of the used diffusiontreatment are described in Rompps Chemie-Lexikon, 8th edition,Franckh'sche Verlagshandlung, Stuttgart.

INDUSTRIAL APPLICABILITY

The present invention provides a burner which is characterized by a highresistance to thermal and corrosive loads.

LIST OF REFERENCE NUMERALS

(1) burner throat

(2) outer burner tube

(3) reactor wall

(4) combustion chamber

(5) inner burner

(6) mixture of carbonaceous fuel and steam

(7) oxygen

(8) protective layer

(9) cooling chamber

(10), (10′) workpiece

(11) adhesive layer

(12), (12′) surface of the adhesive layer

(13) heat insulation layer

1. A burner for the partial oxidation of liquid, carbonaceous fuel withsteam and an oxygen-containing gas, whose outlet orifice is directedinto a combustion chamber, wherein the parts of the outlet orificedirected towards the combustion chamber are wholly or partly providedwith a coating or with a diffusion layer for protection against thermalload and/or corrosion.
 2. The burner according to claim 1, wherein thecoating consists of an adhesive layer and a heat insulation layer, whicheach are applied by a thermal spraying method, such as plasma spraying,wherein the adhesive layer consists of the metal mixture MCrAlY (Mrepresents at least one of the elements Ni, Co, Pt or Pd) and whereinthe heat insulation layer preferably consists of an oxidic sprayingmaterial, in particular of ZrO₂.
 3. The burner according to claim 1,wherein by alitizing, chromizing or siliconizing merely a diffusionlayer is produced in the surface of the workpiece.
 4. The burneraccording to claim 1, wherein the parts of the outlet orifice directedtowards the combustion chamber are wholly or partly provided with acombination of a coating for protection against thermal load and adiffusion layer.
 5. A process for the partial oxidation of liquid,carbonaceous fuel with steam and an oxygen-containing gas, wherein atleast one burner according to claim 1 is used.